1. Field of the Invention
The present invention relates to a .pi./4 QPSK (Quadrature Phase Shift Keying) signal receiver and, more particularly, to a circuit for stabilizing the frequency of a .pi./4 QPSK signal receiver.
2. Description of the Related Art
It is a common practice with a circuit for the above application to stabilize the frequency of the receiver by measuring the frequency of a .pi./4 shift QPSK signal. This brings about a problem that when the mean frequency of the QPSK signal differs from the carrier frequency due to the offset of data included in the signal, a local oscillator cannot be stabilized at a correct frequency.